Performance evaluation of nonlinear control approaches for grid-connected PV systems includes a novel fractional-order terminal-super twisting approach

This paper investigates modern control approaches to improve the energy fineness of grid-connected PV systems. From a two-stage command structure, the first controller regulates the boost converter-based DC side to maintain fast and accurate maximum power point tracking (MPPT) of the photovoltaic (PV) generator under varying climatic circumstances. At this level, a novel nonlinear control approach, called fractional-order terminal super-twisting algorithm (FOTSTA) is introduced for the PV boost converter. The FOTSTA approach is a hybrid strategy characterized by simplicity, high robustness, great efficiency, ease of implementation, does not require knowledge of the mathematical model of the studied system, low cost, and fast dynamic response. A comparative study is conducted with the well-known versions of nonlinear command: sliding mode control and super-twisting algorithm to evaluate the performance of the proposed FOTSTA approach. In the second stage, the model predictive command is applied to regulate the active and reactive power of the three-phase grid-connected inverter-based AC side to their reference values that are generated by the outer loop of the DC link voltage via an anti-windup proportional-integral controller. The simulation was performed in MATLAB using a BM SX150S solar panel. The results demonstrate the competence and moderation of the proposed FOTSTA approach in terms of tracking performance, feasibility, less energy ripples, and robustness against varying solar irradiance conditions. Furthermore, the comparison test reveals a better reflection on the inversion stage, which improves various functionalities assigned to the grid-connected inverter side, namely harmonic pollution compensation and power flow quality from the solar PV power generation source to the grid.